I was lucky to catch the QRM start this morning @ approximately 10 AM Pacific Standard time. It was wide, starting around 3000 kHz up to 10000 kHz.

It starts fast then slows to a crawl. The noise has pronounced high/low bumps as you'll see in the video. Almost like a train with high/low boxcars rolling through ...

The rolling was faster before I started recording.

Once it stops, it is very still with minor drift +/- and is present until approximately 10 PM Pacific Standard time. When it stops rolling, it does not start up again. It present periodically throughout the bands from 80 -> 30 meters.

Before and after 10 AM/PM, it is not present anywhere that I can see.

What would cause rolling QRM like this?

I caught it yesterday and powered-down my house at the breaker only leaving one circuit up for the radio and switching circuits to validate whether or not it was the house. To the best of my knowledge, it is not my house but something in the environment radiating RFI.

Living in Las Vegas, NV, we have a lot of solar rooftops that could perhaps contribute to this in some way. However, it lasts until 10 PM which is far past sunset.

  • Radio FT-950
  • Astron RS-35M power supply
  • Active Mini-Whip antenna
  • 1
    $\begingroup$ Do you live near any factories, especially one that may have a 10 to 10 schedule? Have you tried locating it by driving around with a portable shortwave radio? $\endgroup$
    – Mike Waters
    Jun 1 '18 at 20:24
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    $\begingroup$ I am in a densely populated neighborhood, all houses as far as the eye can see. I will use my Techsun to narrow it down today. Good idea. $\endgroup$
    – user11702
    Jun 2 '18 at 15:07
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    $\begingroup$ Is your whip antenna indoors? If you move it, does the S-meter or the pattern change? $\endgroup$
    – Mike Waters
    Jun 2 '18 at 17:43
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    $\begingroup$ By the way, the fact that these appear at the lowest observed frequency exactly when they "leave" at the highest is a strong indication of them aliasing; so, these signals are almost certainly not at the frequency you think they are. I don't know your radio – can you use it with less receiver gain? Does it have appropriate front-end filtering? If these filters are good enough, you'd be observing something very strong, at which point it might be wise to simply call your spectrum regulatory body (FCC? Are you in the US?) and let them figure this out. $\endgroup$ Jun 2 '18 at 22:17
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    $\begingroup$ The noise is present with a long wire antenna too. I sourced the noise to a neighbors house. With a portable radio, the signal strength grows and eventually overloads the radio when I get in front of the source. $\endgroup$
    – user11702
    Jun 6 '18 at 14:06

I've seen similar 'roving' signals emanating from low quality switching type power supplies, which can generate noise at multiple harmonically related frequencies.

Since you've mostly ruled out local sources, you might have to do a bit of sleuthing with a small directional loop antenna and a portable receiver. A cheap RTL type SDR receiver with a down-converter for HF hooked to the USB port on a laptop PC can work well for this, such as one of the AirSpy radios, as you can monitor lots of radio spectrum at once. A small wire loop antenna maybe 8-12" diameter should provide enough directivity, as long as there's enough signal. The hours of operation suggest maybe a device used by a nearby neighbor who is home during the day - maybe a television or radio power supply, or a charger for a laptop or tablet.

  • $\begingroup$ Welcome! That's a decent first answer. Please consider taking the tour, and we're glad that you're here. BTW the original poster answered his or her own question in one of the comments, and traced the noise to a neighbor's house. Good luck to him or her getting the neighbor to stop using the offending device... $\endgroup$
    – rclocher3
    Aug 27 '18 at 23:41
  • $\begingroup$ Yes, I saw that. I thought the question was mainly 'what' might be causing that type of interference, and I just thought I'd point out a specific type of device I've encountered that generates signals fitting that profile. It's good that he already knows approximately 'where' it is though! That's half the battle. A directional loop antenna can be helpful in tracking 'where' an interfering signal is coming from, especially for signals emanating from further away than next-door. Cheers! :-) $\endgroup$
    – bryon
    Aug 29 '18 at 16:48

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